Variables to harvest of maize hybrids and omission plots of macro-nutrients

Comparing variables harvest presented by hybrids in Table 3 and omission plots in Table 4. The H-59 produced less chaff and grain associated with low weight of 200 grains. In contrast, the Z-60 hybrid produced more straw and grain associated with higher test weight. The Puma 1076 was intermediate as it produced high straw value and weight of 200 grains but grain was low (9.35 t ha^-1).

Table 3 Comparison of means of five agronomic variables by effect of five hybrids. 

^£ PL= peso hectolítrico; PS200= peso de 200 semillas. Letras distintas en columnas son diferentes por Tukey al 5%.

Table 4 Comparison of means of five variables to harvest by the effect of eight treatments with omission plots of macro-nutrients to the soil in maize. 

The treatment of omission of nitrogen (N) had the lowest indicators of production: 9.04 t ha^-1 straw, weighing of 200 grains (53.9 g) and grain (7.09 t ha^-1). Straw production was not affected by fertilization treatments due to omission, of the farmer or complete. The same happened to the weight of 200 grains but omitting the treatment of magnesium (-Mg), numerically the lowest (56.97 g). Strictly speaking, the lack of N (7.09 t ha^-1) and P (9.58 t ha^-1) caused minor grain crops in comparison with the rest of the fertilization treatments. These data confirm the lack of N impact on imbalance of other nutrients according to ^{Ciampitti and Vyn (2011)}.

Relevant interactions H x F

H x F interactions with higher contrast of grain production per hectare were evaluated, which are presented in Table 5. The highest grain yields were obtained with farmer fertilization x hybrid Z-60 with 11.36 t ha^-1, followed by -Ca x Z-60, complete x Puma 1076, -K x Z-60. The hybrid Z-60 is judged as "robust" because it is able to hold "high grain yields" even with omission of calcium (interaction F6H5) and the omission of potassium (F3H5). Instead, the hybrid Puma 1076 scored third of interactions and as superior in statistical terms as the hybrid Z-60 (grain yield 11.30 t ha^-1); but by removing sulfur in the fertilization, affected in a reduced yield of two tons of grain. This low production of maize grain with the Puma 1076 were similar to the H-50 hybrids with the omission of P and H-59 with the omission of Mg (Table 5).

Table 5 Comparison of means of the interactions with relative "higher" and "lower" grain yield of maize in Temascalcingo, State of Mexico. 

Diferencia honesta significativa de 1.68.

Apparent physiological efficiency (EFA) of H-47 and H-59 by omission of macro-nutrients.

The apparent physiological efficiency or EFA is defined as the production of grain obtained in kilograms per kilogram of certain nutrient content in the crop biomass hectare. The word "apparent" is noted because the origin and course of the process of absorption and transport is unknown; being from the complex of soil as native nutrient, due to the fertilizer addition, the mineralization of crop residues and other organic fertilizers by biological fixation, by foliar spray or other income. Unlike the concept of agricultural efficiency or EA, which is eminently practical, which is defined as the ratio of "how many kilograms of maize are grown marginally in one hectare between the kg of a nutrient added to the untreated control."

In this study, we have the hypothesis that the EFA are different for maize hybrids and for unbalanced treatment of soil fertilization under the concept of default macro-nutrients N, P, K, S, Mg and Ca. To calculate the EFA, of the hybrids H-47 and H-59 data were presented in kg ha^-1 of straw production + grain= total dry biomass (0% moisture basis) and harvest index of grain I.C.G (Table 6), the average concentration of mg kg-1 of N-P-K-Mg in grain and straw of H-47 (Table 7) and H-59 (Table 8), concentration ratios N, P, K and Mg in grain/straw of two maize hybrids (Table 9), harvest indices kg ha^-1 of NPKMg in total dry biomass (straw+grain) of two maize hybrids (Table 10), the average content of N, P, K and Mg in kg ha^-1 of the dry biomass in straw and grain of maize H-47 (Table 11), average content in kg ha^-1 of N, P, K and Mg in the dry biomass of straw and maize grain of H-59 contained in kg ha^-1 NPKMg in dry biomass (straw + grain) of two maize hybrids and apparent physiological efficiency (EFA)= kg of grain to 14% moisture/kg of total dry content NPKMg biomass (straw + grain ) two maize hybrids.

The average grain yields in dry basis (0% moisture) was 9.91 t ha^-1 and 8.98 t ha^-1 for the H-47 and H-59, respectively (a ton of difference). The indices of grain (ICG) were virtually identical to the M-59 (0.57) vs H-47 (0.55); but is seen in H-47 in contrast the omission plot (-N) with ICG 0.50, surpassed by all the fertilization treatments, while with the M-59 the opposite happened because the (N) value of 0.58 was higher or equal to the other fertilizer treatments (Table 6). The above shows the genetic load of each hybrid that has adaptive response to the omission of some macro element according to (^{Gallais and Hirel, 2004}; ^{Hefny and Aly, 2008}); and it is useful to adopt the best practices of site-specific fertilization (^{Roberts, 2007}).

With italic bold fonts are distinguished the average concentrations of the respective macro-nutrients of omission regarding the NPKMg for straw and grain of the H-47 (Table 7) and H-59 (Table 8). Values are displayed in italics associated with the decrease due to the omission of a macro-element. Thus, it was associated with the omission of -P and -K to the decrease of concentrations in straw and grain, but not for -N, as it is a plastic nutrient that meets biomass production. For -Mg is inconsistent, since the H-47 itself lowered their concentrations in grain and straw but for the H-59 while the magnesium content in straw was lower (707 mg kg^-1), in grain it was not like that (2 079 mg kg^-1 vs -N, -P and -K, the three of them with lower values). The lack or excess of supply of any particular nutrient leads to imbalance of other essential elements, companion ion, or dysfunction according with ^{Yu-kui et al. (2009)}.

The sale of the grain harvest outside of the farm represents nutrient exports. This principle also applies to the straw when not incorporated into the soil as manure or compost after being tapped to livestock diet. The concentration relations of NPKMg of grain between straw were the first ones to be present, as understanding of the partition in the plant of the macro-nutrients (Table 9), and with higher accuracy the rates of harvest of NPKMg in grain with respect to the total dry biomass (straw + grain); as exported value of nutrient outside of the farm (Table 10).

Table 6 Average of yields of dry biomass (0% straw moisture, grain and total) and grain harvest index (I.C.G) of two hybrids of maize by omission treatments. 

Table 7 Concentrations in mg kg^-1 of N, P, K and Mg in the dry biomass of straw and grain of maize H-47. 

Table 8 Concentrations in mg kg^-1 of N, P, K and Mg in the dry biomass of straw and grain of maize H-59. 

Table 9 Concentration relations of N, P, K and Mg in grain/straw of two maize hybrids. 

Table 10 Harvest index of NPKMg in grain/total dry biomass (straw + grain) of two-hybrids. 

The concentration ratio of macro-nutrients in grain/straw on average for H-47 and H-59 were: of N 1.41 and 1.35, respectively (is explained 1.41 kg of N in grain by 1 kg of N in straw); P of 3.46 and 4.45; K of 0.31 K in both hybrids, Mg 1.65 and 2.06 (Table 9). Sample contrast between P and K; since phosphorus was preferentially oriented to the grain of three to four times more than in the straw; while in potassium the opposite happened because only one third (0.31) was concentrated in the grain. These four macro-elements are mobile on the plant and the differences appear on the lower leaves due to the demand of organs in new formation; but the reason to the partition is mainly explained by genetics and the phenological stage of the crop (^{Ritchie et al., 2002}; ^{Gallais and Hirel, 2004}).

The harvest index or average NPKMg content in maize grain for H-47 and H-59 were respectively: N of 0.64 and 0.63, P of 0.81 and 0.88, K of 0.28 and 0.35, Mg of 0.67 and 0.77. Two large contrasts are observed, first to H-47 with (-N) the N harvest index was only 0.51 vs the control of the farmer of 0.70; and second, for H-59 with (-K) the harvest index of K was 0.13 vs the range of 0.34 to 0.42 of all the fertilization treatments. The International Institute for Plant Nutrition (^{IPNI, 2009}), published for a harvest of 10 t ha^-1 of grain and its straw; harvest rates for NPKMg were: N of 0.66, P of 0.75, K of 0.21 Mg of 0.28; which are equivalent in that grain harvest the amounts in kg of 145N, 30P, 40K and 8mg. Data shown here agree with harvest rates for N and P, which are slightly higher for K and "very high" for Mg (2 to 3 times), indicating possible imbalance by cationic antagonism.

Net values in kg ha^-1 of NPKMg in straw and grain were calculated from the biomass production and its chemical concentrations, and is presented for the H-47 in Table 11. It is noteworthy recalling the average plot was almost 10 t ha^-1 of grain. The contents extracted in kg ha^-1 in straw of N and K is relevant for both hybrids H-47 and H-59 with ranges of about 101-126 of N and 162-101 of K, respectively. In general, the value showed in bold italics of the omission of a macro-nutrient was reflected in lower content taken in the straw and grain. Thus, for -N of the H-47, the contents in kg ha^-1 of N in straw was of 116 vs the average 126.5 and grain of 120 vs the mean of223. Similarly with -N for the H-59, the contents extracted in kg ha^-1 of N where in straw of70.5 vs the average of 101, and grain of 145.3 vs the average of 172.2.

Table 11 Contents of N, P, K and Mg in kg ha^-1 in dry biomass of straw and of grain maize H-47.