FAQ: Nutrient management

42. Is green manuring possible in no-till system?
We can grow a green manure crop in no till system with the help of ZT machine along or before planting the rice crop. Green manure crop can be killed by use of any broad-spectrum herbicide, if GM crop is seeded alone. The broad-spectrum herbicide is helpful in killing the other weeds growing with green manure crop. Rice crop can be transplanted or dry seeded directly after a green manure crop. If rice and GM crops are planted simultaneously or as relay crops, use of herbicides such as 2,4-D is helpful in killing GM crop in presence of rice. In this way, we can secure the benefits of atmospheric nitrogen fixation, weed control and organic materials.

43. How to top-dress urea in mulched plots of wheat/rice?
Top dressing of nitrogenous fertilizers is not easy in fields mulched with residues of the previous crop. Residues retain for itself top dressed N and do not allow it to reach plants roots. In order to avoid temporary immobilization of N, it is appropriate to deep place the total fertilizer at about 10 cm as a single basal dose or chisel-in the fertilizer at the same depth.

44. Do placement of fertilizers and seed together in same slit adversely affect seed germination?
Normally, South Asian farmers apply 120kgN, 20kgsP and K and 5kgsZn /ha, Nearly half of the total fertilizer requirement (N, P, K and NZ) is applied as a basal dose. These chemical fertilizer nutrients are delivered from the fertilizer box through a tube into slits made with zero-till openers for placement of seed. Thus seed and fertilizer are in the same grove but machine design places fertilizer a small distance below seed to avoid seed damage. Whenever, a full dose of N is applied as basal, it is advised to apply fertilizer between two seed rows, else it may reduce germination by 5-6% percent. Thus all the fertilizer nutrients can be placed in just one pass of the drill during seeding operation. One time deep placement of fertilizers in sandy loam and other finer textured soils optimizes the nutrient -water interactions for higher yields under supply driven irrigation systems.

45. What is the appropriate method for fertilizer application in surface seeded crops?
Surface seeded crops can be fertilized through band placement of fertilizer nutrient along the seed rows or by broadcasting the fertilizers when fields come to dry conditions, followed by irrigation. It is better to first kill weeds and then go in for application of fertilizer nutrients. Fertilizer can be dribbled or band placed with machine during an intercultural operation in line seeded crop.

46. How we can increase the fertilizer use efficiency of surface seeded crop?
For improving the efficiency of externally applied fertilizer nutrients, practices that affect population of weed, loss of nitrogen, and movement of nutrients to lower root zone based on scientific concepts and principles be followed.

47. Why single band placement of fertilizer is better than their split application?
Routinely, nitrogenous fertilizers are applied in splits to match crop nutrient requirements at different plant growth stages. However, for optimum plant growth, nutrient- water interactions play a pivotal role. In irrigation systems that are more supply driven, our experiences of working in the region suggest that farmers most often are not able to timely supply nutrients and water. For the antecedent and prevailing soil moisture regimes it is therefore a better strategy to apply the total N just at the planting time for optimum nutrient-water interactions.

48. Will total application of fertilizer in a single dose in high water conditions affect their losses?
All fertilizer nutrients are not equally mobile in soils. Nutrients such as phosphorus and zinc etc. are only slightly mobile. A relatively mobile nutrient such as NO3-N under aerobic conditions is able to move deep into soil profile and outside the reach of the active root system into aquifer. Under anaerobic conditions water table close to soil surface such as in puddled submerged soils NO3-N gets transformed into NH4+ form and is adsorbed on the negatively charged clay particles and not able to move freely with water reducing N losses. Therefore, total N is often recommended for a single deep placement in rice and could even be practiced with advantage in wheat and other upland crops to harness synergy of nutrient-water interactions for greater photosynthetic activity.

49. How to overcome yellowing/ chlorosis in wheat caused by water logging conditions?
Leaf chlorosis/ yellowing from temporary waterlogging is generally more intense in wheat planted in partially reclaimed alkali soils. In other situations poor reduced aeration lead to sudden imbalance in nutrition of iron and phosphorus and other nutrients. In order to ameliorate and overcome the ill effects of leaf yellowing, farmers general apply 10-15 kg urea or diammonium phosphate with advantage.